In the 1960s a major reason put forth for continued United States involvement in the Vietnam war was known as the Domino theory.

In the 1960s a major reason put forth for continued United States involvement in the Vietnam war was known as the Domino theory. The supporters of this theory made the following statements: Each county that falls to communism leads to another country falling to communism. If south Vietnam becomes communist, then the rest of Southeast Asia will soon become communist. South Vietnam will fall to the communist North Vietnamese and the major powers The United States must continue to fight to keep South Vietnam a free democratic nation.

Based on seven step for arguments 

Step 1. Convert the argument into standard form. (List the premises first, followed by the conclusion.)

Step 2. Test the argument for its reasoning strength to see whether it is valid or invalid. (Assume the premises to be true, and ask yourself whether the conclusion must also be true when those premises are assumed true. Is a counterexample to the argument possible?)

Step 3.  Is the argument valid?

  If yes, go to Step 4.

  If no, go to Step 5.

Step 4. Is the (valid) argument also sound? That is, are the premises true in the actual world?

4a. If the argument is valid and if all of the premises are true in the actual world, then the argument is also sound.

4b. If the argument is valid, but one or more premises can be shown to be either false or not capable of being verified in the actual world, then argument is unsound

Step 5. Is the (invalid) argument inductive or fallacious? (How likely will the conclusion be true when the premises are assumed true?)

5a. If the conclusion would likely be true because the premises are assumed true, the argument is inductive.

5b. If the conclusion would not likely be true even when the premises are assumed true, the argument is fallacious. (Keep in mind that a fallacious argument can be made up of Individual claims that are themselves true in the actual world.)

Step 6. Determine whether the premises in your argument are either true or false.

Step 7: Make an overall assessment of the argument. That is, describe the argument’s strength of reasoning in conjunction with the truth conditions of the argument’s premises. For   example, is the argument inductive with all true premises? Is it inductive with some false premises? Is it fallacious with a mixture of true and false premises, and so forth? Remember that an inductive argument with premises that are all true is stronger than a valid argument with one or more false premises.)